There is another alternative - Mattroberts is correct that the front fence is required to keep it together, but with some ingenuity you could have both.
First you'll need to make the sled long enough to accomodate the blade AND the largest sized cuts you think you'll make REGULARLY, then make the front fence movable.
If it was me I'd use a pin hinge of some kind on one outer edge so the front face swings out the way to allow you to slot it into place on the blade, then swing the front fence back and lock it down.
If you make the fence an L shape with the horizontal at the back you could put some T nuts countersunk into the sled base underneath and use some short bolts (with homemade handles) to go through the flat part of the L and into the T nuts to lock the front fence down. Make sure once they are fully tight to grind off the excess so it doesn't catch the smooth surface.
If you are using a smaller table saw you could add longer stabilizers either side of the tablesaw surface to increase the capacity front to back - either stable hardwood or steel angle. I've seen this done on several smaller tablesaws to allow people to cut sheet material through it.
Either that or take the guard and extraction off the blade and incorporate it into the sled system - hmm... a central flat bar over where the blade cuts, made of perspex for visual clarity, a couple of wood beams attached to stiffen it then add those sort of draft excluder bristle things attched both sides and down to the sled to create a sort of "movable curtain barrier" so wood will slid in and out and they will move as you cut, but will help keep the sawdust inside that area and hook up a vaccum to a port in the perspex.
Won't be 100% but it'll get the worst of it I guess?
what do you think?
